Visualizing Fertisphere Dynamics: High-Resolution Chemical Imaging Reveals Distinct Phosphorus Release Patterns of Fast- and Slow-Acting Fertilizers

Phosphorus (P) deficiency in soils is commonly addressed through phosphate fertilizers, yet millimeter-scale fertisphere dynamics governing fertilizer–soil interactions remain poorly understood, constraining P-use efficiency optimization. This study employed high-resolution chemical imaging to visualize P release patterns, pH dynamics, and acid phosphatase activity in acidic soil fertispheres of contrasting fertilizers: calcium hypophosphite (fast-acting) and apatite (slow-acting). Calcium hypophosphite exhibited rapid dissolution with peak P flux (442 pg cm–2 s–1) at patch edges within 24 h, coinciding with pH elevation that suppressed enzyme activity. Complete dissolution occurred within 48 h. Conversely, apatite released P steadily over 99 days (peak flux: 13.6 pg cm–2 s–1), with release zones shifting inward as H+ consumption generated alkalinization cores. Temporal analysis revealed a 22-day lag between P flux and pH maxima (R = 0.66). These mechanisms demonstrate the importance of matching fertilizer solubility with soil chemistry for precision P management, maximizing bioavailability while minimizing environmental losses.